It is possible that the main title of the report Marfan Syndrome is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.
As Jenny points out, being able to lisp the alphabet song at age two has little to do with 'knowing' the alphabet. And, yes, most children learn the letters by sight and sound in kindergarten, although most are capable of learning this information sooner if diligently taught by parents or others.
Phonological awareness, the ability to detect or manipulate the sounds in words independent of meaning, is a precursor to reading. The added letter knowledge training component includes teaching children the letters of the alphabet and making an explicit link between letters and sounds.